1. Field of the Invention
The present invention relates to cylindrical locks of the type installed in bored openings in a door. More particularly, the present invention relates to the highest quality and strongest locks of this type designed for use with lever handles where abusive mechanical loads can be applied to the lock mechanism through the lever handle.
2. Description of Related Art
Doors are much easier to open when the door handle is shaped as a lever handle rather than a conventional round knob. For this reason, lever handles are preferred in some applications, and they may be required under applicable regulations for certain doors in public buildings to facilitate access by the disabled and the elderly.
However, the lever shape of the door handle allows much greater force to be applied to the internal locking mechanism of the door than can be applied with a round knob. In most door locks, the lock mechanism prevents the knob from being turned when the door is locked. When a round door knob is replaced by a lever handle, the greater leverage available from a lever handle may allow a vandal or thief to break the internal components of the lock mechanism by standing or jumping on the lever end of the handle. This problem is particularly acute for cylindrical locks, which have less internal room than mortise type locks to accommodate heavy-duty locking components.
Another problem relates to the unbalanced shape of a lever handle, which tends to cause the lever handle to droop. A conventional round doorknob is balanced around the rotational axis of the handle. Thus, it takes relatively little force to return the handle to the rest position. This return force is usually provided by the latch rod return springs in the lock. A lever handle, however, requires much more force to return it to the level position. Sufficient force cannot be provided by the latch rod return springs, so most lever handle designs incorporate auxiliary lever handle return springs.
Because the lever handle return springs are large, and because there is limited space inside the lock, the auxiliary lever handle support springs have heretofore been located in the rose. While this is effective, locating the lever handle return springs in the rose produces a thick rose that is considered by some to be relatively unattractive.
The visual symmetry of a round doorknob means that it is not critical that the knob return exactly to the rest position when the handle is released. However, if a lever handle does not fully return to the level rest position, it appears to droop. Such visual droop is particularly objectionable. A rest position that is slightly above level, however, is generally not considered to be objectionable.
To avoid visual droop, as a result of normal wear or component tolerances, it would be desirable for the rest position of the lever handle to be slightly above horizontal. However, heretofore it has been difficult to arrange for the lever handle to return to a position above level without constructing the lock in two different versions for left-hand swing and right-hand swing doors or without placing the stops in the rose.
A conventional lock can be installed in either a left-hand swing or a right-hand swing door by flipping the lock top for bottom. This keeps the locking side of the lock mechanism on the same side of the door, while allowing for both the left-hand swing and right-hand swing operation. If the stop position were to be located in the lock mechanism, however, this rotation about a horizontal axis would cause the above-level stop position to reverse to an objectionable below-level position. Requiring separate locks for left and right-hand swing doors, however, is undesirable as it increases inventory costs and results in confusion and delay when the wrong lock is ordered.
Accordingly, the stops are usually placed in the rose. This allows the rose to be reversed relative to the lock body, as needed to always keep the top of the rose at the top regardless of whether the lock is installed in a left-hand or right-hand swing door. Placing the stops in the rose, however, is undesirable as it requires that the rose be made thick to accommodate the stops.
When the rose is used to provide the stops to limit handle motion and to house the return springs, it is necessary to anchor the rose relative to the door. Usually this is done with through-bolts, which connect roses on opposite sides of the door and pass outside of the main hole for the lock body. Through-holes, however, require a large diameter rose to cover these holes. Such a large diameter rose is considered by some to be unattractive and the large diameter increases the cost of the rose.
Another problem with prior art lever handle cylindrical locks arises as a result of the method used to attach the handle to the lock mechanism. Generally, the handle slides over a shaft and is captured by a spring loaded capture piece. The capture piece must have some clearance from the hole that captures it, and this clearance allows axial motion between the shaft and the handle. This motion is perceived as a xe2x80x9cloosexe2x80x9d handle by the user and is undesirable. Often, there is also some relative motion between the shaft and the lock mechanism as well, which contributes additional objectionable axial motion between the handle and the door. It is highly desirable to reduce or eliminate this axial endplay between the handle and the lock mechanism.
Bearing in mind the problems and deficiencies of the prior art, it is therefore an object of the present invention to provide a lock mechanism for use with lever handles that is strong and resistant to abuse.
It is another object of the present invention to provide a lock mechanism for use with lever handles that does not require boring through-holes.
A further object of the invention is to provide a lock mechanism for use with lever handles that uses thin and small diameter rose plates.
It is yet another object of the present invention to provide a lock mechanism for use with lever handles that has reduced endplay between the handle and the lock body.
It is still another object of the present invention to provide a lock mechanism for use with lever handles that can be more completely disassembled and repaired in the field.
Still other objects and advantages of the invention will in part be obvious and will in part be apparent from the specification.
The above and other objects, which will be apparent to those skilled in art, are achieved in the present invention, which is directed to a lock mechanism that includes a lock core with a bearing that fits into a first opening bored through the faces of a door and a latch mechanism that fits into a second opening bored perpendicularly from the edge of the door into the first opening.
The latch mechanism includes a latch bolt frame adapted to fit within the second opening. The latch bolt frame is removably attached to the lock core with a rigid connection. The rigid connection between the latch bolt frame and the lock core prevents rotation of the lock core relative to the door. This provides an extremely robust anchor between the lock core and the door so that through-bolts are not required. Because through-bolts are not needed, the rose can have a small diameter, producing a pleasing external appearance for the lock mechanism.
The latch bolt frame may be constructed as a tube enclosing the latch mechanism. The latch bolt frame is sufficiently robust to prevent significant rotation of the lock core during the application of 1000 inch-pounds of torque to the lock core by the lever handle.
The latch mechanism includes a latch bolt, which slides axially inside the latch bolt frame between extended and retracted positions. A sleeve is mounted in the bearing of the lock core, perpendicular to the latch bolt frame. The sleeve includes a shaft portion that extends outward from the bearing and a lever handle is mounted thereon. The sleeve is operatively connected to the latch mechanism to move the latch bolt between the extended and retracted positions as the sleeve is rotated by the lever handle.
A locking piece is mounted in the sleeve so that it can slide axially from a locked position to an unlocked position. The locking piece includes at least one locking lug, and preferably two locking lugs that project radially outward from the sleeve. The locking lugs engage the lock core in the locked position to prevent the lever handle and sleeve from rotating relative to the lock core. By making the locking lugs robust and extending them outward beyond the radius of the sleeve, the forces on them are reduced and they are able to withstand significant abuse, as compared to prior art designs.
In the preferred embodiment of this invention, the locking piece includes a latch driver at an end thereof. The handle turns the sleeve, the sleeve turns the locking piece and the locking piece turns the latch driver. The latch driver forms the operative connection between the sleeve and the latch mechanism by engaging the latch mechanism to drive the latch bolt when the locking piece is in the unlocked position. The latch driver disengages from the latch mechanism when the locking piece is in the locked position.
In the most highly preferred design, the locking piece also includes a key driven piece extending through the locking piece. The key driven piece engages the latch mechanism when the locking piece is in the locked position to allow the latch rod to be retracted by a key while the locking piece remains in the locked position.
Inside the lock core is a spring return for returning the lever handle to a level position, or, more preferably, to slightly above level. The spring return includes a plurality of coil springs, preferably two on each side of the lock core. The coil springs are located in curved contact with an inner surface of the cylindrical lock core. Thus, no portion of the spring return mechanism needs to be located within the rose. This allows the rose to be very thin to provide a pleasing appearance for the lock mechanism.
To provide the strongest construction, the latch bolt frame extends completely through the lock core. In this aspect of the invention, the spring return includes four coil springs organized into two pairs. The pairs of coil springs are located on opposite sides of the latch bolt frame, but still within the lock core.
To reduce the angular distance that the lever handle must be turned, while permitting complete retraction of the latch bolt, the latch mechanism is constructed with a retractor mechanism that retracts the latch bolt and a latch retraction amplifier comprising a retractor arm pivotally attached to the latch bolt frame at one end thereof and contacting the latch bolt at an opposite end thereof. A retractor link extends between the retractor mechanism and the retractor arm. The link acts upon the retractor arm to amplify the linear motion of the latch rod such that the latch bolt moves to the completely retracted position when the lever handle is rotated by no more than forty-five degrees.
The lock core defines an angular mounting orientation of the lever handle relative to the lock core when the lever handle is at rest. The latch bolt frame engages the lock core at an angle less than 180 degrees relative to the angular mounting orientation of the lever handle on the lock core. In this way, the lever handle is held at an angle greater than zero above horizontal when the latch bolt frame is horizontal.
In another aspect of the present invention, endplay is eliminated from the connection of the handles to the lock. To accomplish this, the lever handle is securely mounted on the shaft portion of the sleeve to prevent axial motion of the lever handle relative to the sleeve. The sleeve includes an enlarged portion having a diameter greater than an inner diameter of the bearing receiving the sleeve. The enlarged portion of the sleeve is held in contact with a face surface of the bearing by a retaining collar. The enlarged portion of the sleeve cooperates with the face surface of the bearing to prevent axial motion of the sleeve relative to the lock core.
In still another aspect of the present invention, the retaining collar is provided with one or more lock notches, one of the lock notches engages a lock pin to prevent the retaining collar from being removed. In the preferred embodiment of the invention, the lock pin includes a head and the lock core includes a recess that receives the head of the lock pin. This allows the retaining collar to be tightened into position on the lock core. The head of the lock pin is then extended outward from the recess in the lock core and into engagement with the lock notch in the retaining collar after the retaining collar has been tightened.
In yet another aspect of the present invention, the lock core includes a cylindrical center core and a pair of bearing caps. Each of the bearing caps includes a bearing. The bearing caps are connected to the lock core with removable fasteners to allow the lock core to be disassembled.